Dye-Doped ZnO Microcapsules for High Throughput and Sensitive Optofluidic Micro-Thermometry

Abstract

The main objective of this work is to show the proof of concept of a new optofluidic method for high throughput fluorescence-based thermometry, which enables the measure of temperature inside optofluidic microsystems at the millisecond (ms) time scale (high throughput). We used droplet microfluidics to produce highly monodisperse microspheres from dispersed zinc oxide (ZnO) nanocrystals and doped them with rhodamine B (RhB) or/and rhodamine 6G (Rh6G). The fluorescence intensities of these two dyes are known to depend linearly on temperature but in two opposite manner. Their mixture enables for the construction of reference probe whose fluorescence does not depend practically on temperature. The use of zinc oxide microparticles as temperature probes in microfluidic channels has two main advantages: (i) avoid the diffusion and the adsorption of the dyes inside the walls of the microfluidic channels and (ii) enhance dissipation of the heat generated by the focused incident laser beam thanks to the high thermal conductivity of this material. Our results show that the fluorescence intensity of RhB decreases linearly with increasing temperature at a rate of about −2.2%/°C, in a very good agreement with the literature. In contrast, we observed for the first time a nonlinear change of the fluorescence intensity of Rh6G in ZnO microparticles with a minimum intensity at a temperature equal to 40 °C. This behaviour is reproducible and was observed only with ZnO microparticles doped with Rh6G.

Self-Cleaning and Shape-Adaptive Triboelectric Nanogenerator-Contained TiO2 Nanoparticle Coating

“…2 mL of 10 ppm RhB is sprayed on the surface of the SAP film to simulate the pollution of TENGs during use. The solar simulator (Zolix, LCSS500-NMNY, 11.2 mW cm –2 ) , is used as the light source to the contaminated SAP film vertically. The absorption intensity is measured every 5 min with an ultraviolet–visible spectrophotometer (Shimadzu UV 3600).…”

High-Sensitivity Microthermometry Method Based on Vacuum-Deposited Thin Films Exhibiting Gradual Spin Crossover above Room Temperature

“…With the continuous advancement of micro- and nanotechnologies, the development of noninvasive thermometry techniques, capable of measuring and imaging the temperature at the micro- and nanoscale, is of paramount importance for various technological fields, such as photonics, microelectronics, and biomedicine. − The most common, industry standard, thermal imaging methods rely on optical thermometry techniques, which consist in tracking an optical response (Planck blackbody emission, − Raman scattering, luminescence, or optical reflectivity − ) of the investigated object's surface to a temperature change . Importantly, an extension to these conventional thermo-optical techniques can be provided by deposition on the investigated surface of temperature-sensitive materials, such as liquid crystals or luminophores, ,,− to enhance the thermally induced optical contrast of the surface and then the achievable thermal sensitivity and the accuracy of the temperature measurement.…”

Effect of ZnO surface morphology on its electrochemical performance

“…[11][12][13] For two-dimensional forms of ZnO, we nd pellets and sheets, 14,15 while spheres and owers are examples of three-dimensional forms of ZnO. [16][17][18] In general, several synthetic methods are used to utilise ZnO in different forms, such as microuidic, hydrothermal, electrochemical, and sol-gel methods. [19][20][21] However, the most used method is the electrochemical one, where different forms of ZnO are obtained by varying the conditions.…”